Miniaturized Pumps and Gauges for Ultra-High Vacuum Microsystems

Shiyang Deng

About the Event

Abstract:
This thesis describes two types of elements: (i) miniaturized RF electron traps for magnet-less ion pumps, and (ii) miniaturized cold cathode gauges to measure vacuum levels.
The first-generation RF electron trap formed a 0.7 cm3 electron active volume between two perforated RF electrodes spaced 0.7 cm apart. An RF signal of various power levels and at 143.6 MHz was applied across two RF electrodes to trap electrons that were supplied by an electron gun. It was found experimentally that the steady state electrode potentials (SSEPs) on electrodes near the trap became more negative after applying certain RF power levels, which indicated higher electron density within the trap. The observed trends aligned well with the modeled trends. The electron density within the trap was estimated to be 3 x 105 cm-3, which is ~1000x the electron density in the electron beam as it exits the electron gun. The second-generation RF electron trap is refined in structure to have 10x finer perforated RF grid electrodes, a higher trap-to-device volume ratio, simplified electrode compositions and RF characteristics, and a tunable operating frequency. The experimental results estimate that the electron density is 2.24 x 106 cm-3 in the center of the RF electron trap when the trap is operated at 96.9 MHz with a transmitted RF power of 0.273 W. Both RF electron traps represent successful demonstrations of a method for trapping electrons without using a magnetic field.
Seven preliminary cold cathode gauge (CCG) designs with an internal volume of less than 1 cm3 were developed. Analysis showed efficient electron spiraling with a DC operating voltage lower than 1000 V. Four CCG designs were further refined to analytically demonstrate better electron spiraling capability while also fulfilling manufacturability requirements. A magnetron design is modified from the refined magnetron design and fabricated with 3D printing techniques for performance characterization. The miniaturized CCGs are at least 10x smaller than commercially available CCGs.